Add a service

Tools

systemctl – Control the systemd system and service manager

list-timers [PATTERN...]	List timer units currently in memory, ordered by the time they elapse next.
enable UNIT..., enable PATH...	Enable one or more units or unit instances. This will create a set of symlinks, as encoded in the “[Install]” sections of the indicated unit files. After the symlinks have been created, the system manager configuration is reloaded (in a way equivalent to daemon-reload), in order to ensure the changes are taken into account immediately.
disable UNIT...	Disables one or more units. (won’t start automatically)
mask UNIT...	Mask one or more units, as specified on the command line. This will link these unit files to /dev/null, making it impossible to start them. This is a stronger version of disable, since it prohibits all kinds of activation of the unit, including enablement and manual activation. Use this option with care.

Usual tasks

systemctl status postfix
systemctl reload-or-restart postfix

Get a list of enabled services

systemctl list-unit-files | grep enabled

Disable a service

systemctl disable <service>

Get systemd version

# systemctl --version
systemd 239

List timers

systemctl list-timers --all
systemctl list-timers *apt*

journalctl – Query the systemd journal

journalctl pipes its output to the less command, which shows your logs one page at a time in your terminal.

-f, –follow	Show only the most recent journal entries, and continuously print new entries as they are appended to the journal.
-e, –pager-end	Immediately jump to the end of the journal inside the implied pager tool.
-r, –reverse	Reverse output so that the newest entries are displayed first.
-q, –quiet	Suppresses all informational messages (i.e. “– Journal begins at …”, “– Reboot –“), any warning messages regarding inaccessible system journals when run as a normal user.
-u,–unit=UNIT|PATTERN	Show messages for the specified systemd unit UNIT (such as a service unit), or for any of the units matched by PATTERN. This parameter can be specified multiple times.
–user-unit=	Show messages for the specified user session unit.
-S, –since=, -U, –until=	Start showing entries on or newer than the specified date, or on or older than the specified date, respectively.
–disk-usage	Shows the current disk usage of all journal files. This shows the sum of the disk usage of all archived and active journal files.
–rotate	Asks the journal daemon to rotate journal files.
–vacuum-size=, –vacuum-time=, –vacuum-files=	Removes the oldest archived journal files until the disk space they use falls below the specified size/older than/specified number of separate journal files
-x, –catalog	Augment log lines with explanation texts from the message catalog. This will add explanatory help texts to log messages in the output where this is available.

Show journal and follow

journalctl -f

Show journal and follow, showing only a certain unit

journalctl -f -u NetworkManager
journalctl -f -u pvedaemon

Show today’s logs associated to a certain unit

journalctl -S today -u sanoid.service
journalctl -f -S today -u sanoid.service -u syncoid.service

Immediately jump to the end of the journal inside the implied pager tool

journalctl -e 

Get the log at a specific time

journalctl --since "2020-08-22 23:15:00" --until "2020-08-22 23:45:00"

List boots

journalctl --list-boots

Show all messages from this boot (and last boot)

journalctl -b
journalctl -b -1

From: https://wiki.archlinux.org/index.php/Systemd/Journal

https://www.freedesktop.org/software/systemd/man/journalctl.html

Clear logs

https://linuxhandbook.com/clear-systemd-journal-logs/

networkctl – Query the status of network links

networkctl list
networkctl status -a

timedatectl – Control the system time and date

timedatectl may be used to query and change the system clock and its settings.

$ timedatectl
               Local time: Tue 2021-10-12 12:06:50 CEST
           Universal time: Tue 2021-10-12 10:06:50 UTC 
                 RTC time: Tue 2021-10-12 10:06:50     
                Time zone: Europe/Berlin (CEST, +0200) 
System clock synchronized: yes                         
              NTP service: active                      
          RTC in local TZ: no

timedatectl list-timezones

timedatectl set-timezone Europe/Berlin

$ timedatectl status
$ timedatectl timesync-status
$ timedatectl show-timesync --all

$ vi /etc/systemd/timesyncd.conf
$ systemctl restart systemd-timesyncd.service

infos: https://wiki.archlinux.org/title/systemd-timesyncd

systemd-resolve

systemd-resolve – Resolve domain names, IPV4 and IPv6 addresses, DNS resource records, and services

systemd-resolve --status
systemd-resolve debian.org
systemd-resolve 130.89.148.77
systemd-resolve 2603:400a:ffff:bb8::801f:3e

https://wiki.archlinux.org/index.php/Systemd-resolved

systemd-resolve --flush-caches
systemd-resolve --statistics

systemd-analyze – Analyze and debug system manager

As bootchart as been merged in systemd, it is possible to plot the boot sequence to discover what is taking time.

systemd-analyze plot > systemd-analyze-ares.svg

systemd/Timers

systemctl list-timers

systemctl status sanoid.timer
sudo systemctl enable sanoid.timer
sudo systemctl start sanoid.timer

https://wiki.archlinux.org/title/Systemd/Timers

Random

Important folders

/etc/systemd/

Units

man systemd.unit